A simple method for determining light transmittance of polymer films used for packaging foods

Sensitive components of food may undergo degradation reactions when subject ed to light. The packaging of the food may slow down such reactions by abso rbing and reflecting a fraction of the incident light. Riboflavin is a ligh t-sensitive vitamin and undergoes first-order degradation when subjected to visible light. Rate constants of this reaction were evaluated under 20W co olwhite light at pH = 9.0 at 25 degreesC, with no light shielding or by shi elding the light with methylcellulose films. Based on this photodegradation reaction, a new model was proposed to define percentage light transmittanc e of methylcellulose films. Depending on composition, the percentage transm ittance was in the range 66-96%. Variation of light transmittance was expla ined in terms of solubility and crystallinity. (C) 2001 Society of Chemical Industry.